Estimate your due date, current week, trimester, and key milestones from a single LMP date. Adjusts for cycle length and updates live.
Results update live as you change values.
Estimated Due Date
Current week
—
Trimester
—
Days pregnant
—
Days remaining
—
| Milestone | Week | Date | Status |
|---|
The Formula
We use Naegele's rule: due date = LMP + 280 days. The 40-week timeline counts from the first day of your last period rather than conception, because that date is easier to remember.
We then adjust for cycle length — if your cycle is longer or shorter than the typical 28 days, ovulation (and conception) shift accordingly, which moves the estimated due date.
Pregnancy Math
About This Tool
A pregnancy calculator turns the first day of your last menstrual period into a complete pregnancy timeline — due date, weeks pregnant, current trimester, and key prenatal milestones — all in one view.
The math is based on Naegele's rule, used by clinicians since 1830: add 280 days (40 weeks) to the LMP. Because ovulation timing shifts with cycle length, we adjust the result if your cycle isn't the textbook 28 days.
Use it to plan prenatal appointments, anticipate scans, track milestones (heartbeat at ~6 weeks, anatomy scan at ~20 weeks, full term at 39+), and answer the most-asked question of all: when's the baby due?
Due Date in Seconds
One LMP date and you have your EDD.
Live Weekly Progress
See exactly where you are in the 40-week journey.
9 Key Milestones
From heartbeat to full-term — dates calculated for you.
Cycle-Length Aware
Adjusts when your cycle isn't a standard 28 days.
100% Free & Private
No data leaves your browser. No sign-up needed.
Trimester Tracker
Know instantly which trimester you're in.
Just two inputs separate you from your full pregnancy timeline.
Pick the first day of your last menstrual period — not the last day. This is the standard reference point.
Most people use the default 28 days. If you know your cycle is shorter or longer, set it here for a more accurate EDD.
The big number is your estimated due date — when baby is most likely to arrive (give or take ~2 weeks).
See exactly which week and trimester you're in. Useful for booking scans and prenatal classes.
The schedule tab maps every key milestone — heartbeat, gender scan, viability, full term — to a real date.
A first-trimester ultrasound is the most accurate dating tool. Use this calculator as a starting estimate, not a final answer.
Everything you need to know about pregnancy dating and milestones.
The standard method (Naegele's rule) adds 280 days — 40 weeks — to the first day of your last menstrual period. We then adjust for cycle length so people with cycles shorter or longer than 28 days get a more accurate result.
Only about 5% of babies arrive on their exact due date. Most arrive within 2 weeks either side. A first-trimester ultrasound (8–12 weeks) is the most accurate dating method, with a margin of ±5 days.
First trimester: weeks 1–12. Second trimester: weeks 13–26. Third trimester: weeks 27 through birth (usually week 40).
An early ultrasound is the most reliable alternative — it dates the pregnancy by measuring the embryo. If you know your conception date, add 266 days to it for an estimated due date.
Yes. If your cycle is 35 days, ovulation happens later — about day 21 instead of day 14. That shifts conception (and your due date) by a week. The calculator handles this adjustment automatically.
LMP is far easier to remember and verify than the exact day of conception, which most people don't track. Counting from LMP gives a consistent reference point that all healthcare providers use.
The American College of Obstetricians and Gynecologists defines early term as 37–38 weeks, full term as 39–40 weeks, late term as 41 weeks, and post-term as 42+ weeks.